Friction-wheel regulating gear



Oct. 12, 1948.

Filed Aug. 13, 1945 2 Sheets-Sheet 1 TTOR//EY Oct. l2, 1948. E. KRl-:Bs

FRICTION WHEEL REGULATING GEAR 2 Sheets-Sheet 2 Filed Aug. 13, 1945 Patented Oct. 12, 1948 FRICTION-WHEEL REGULATING GEAR Ernst Krebs, Zurich, Switzerland Application August 13, 1945, Serial No. 610,4391/2 In Switzerland August 28, 1944 (Cl. 'i4-200) Claims. 1

This invention relates to friction-wheel regulating gears.

K. There are already known friction-wheel regulating gears in which a friction-Wheel having aange on both sides is arranged between two cone discs which are spaced apart, the said flanges being arranged to face the faces of the two discs and keeping to the same track. The alteration of the transmission ratio is effected by moving the friction wheel, the points of contact being displaced on a track which passes along the faces of the discs and through the Centers. This arrangement makes possible a construction with comparatively small dimensions and favourable conditions for being fitted into machines and the like. However, considerable diiculties are involved in the production and pressing of the two cone discs to the friction wheel which, in order to avoidan unnecessarily large amount of wear of the friction Wheel and the cone discs, should depend upon, i, e., be variable with, the magnitude of the transmitted torque. Special additional devices have to be provided which produce the pressing of the cone discs to the friction wheel and 1 ensure the starting of the gear in every position. As a result, the construction of such friction-wheel regulating gears, which are very eiiicient in themselves, is considerably complicated. This very important disadvantage is eliminated by the present invention.

The subject matter of the present invention is a friction wheel regulating gear having two coaxialr spaced cone discs one of which is.driven by Va ldriving machine whilst the other drives the shaft rwhich is to be driven',`between which cone discs there is `displaceably arranged a frictionwheel transmission device for the purpose of altering the gear ratio, the saidr gear being characterised by the feature that its driving-side part, its driven-side part and the friction-wheel transmission device are each constructed as a structural unit, and that the friction-wheel transmisH sion 'device has two discs, each with a frictionbead, which discs are coupled together with regard to rotation but are axially displaceable in relation to each other. O-ne of the beads lies on a point on a conical-surface line of the drivingside cone disc and the other of the beads lies on a point on a conical-surface line of the driven-side cone disc, which conicalfsurface line lies crosswise, opposite and parallel to the conical-surface line of the driven-side cone disc. The beads are urged apart and against the two cone discs by spring means, and the mutually displaceable discs are mounted in a supporting ring, which is arranged on rollers that are displaceably guided in a guide which is parallel to the conical-surface lines of the cone discs on which lines the contact with the cone discs 'takes place, there being provided `for altering the gear ratio a shifting device, by means of which the rollers which carry the lsupporting ring can be displaced in their guide within two limiting positions.

Advantageously there is provided, both on the driving-side part and on the driven-.side part, a transmission gear which enables a high-speed en,- gine to be provided as the driving machine.

The invention is illustrated by way of example by the accompanying drawings of which- Fig. l is an axial section through a frictionn wheel regulating gear;

Fig. 2 is a section on lthe line II-II of Fig. 1,y the driving device for the shifting device being omitted;

Fig. 3 is a section on the line III-III of Fig. 2;

Fig. 4 is an elevation of one clutch member in the axial direction;

Fig. 5 is a corresponding side elevation, partly in section;

Fig. 6 is an elevation of the same clutch member from the side opposite to that of Fig. 4;

Fig. 7 is a side elevation of the other clutchk member, partly in section;

Fig. 8 is a corresponding elevation in the axial direction; and

Fig. 9 is a side elevation of the two clutch memi bers in engagement with each other, partly in section,

I denotes a casing which is closed by a lid 2 on one side, on the right hand side in the embodiment represented. In the embodiment represented, that is to say on the right hand side, there is accommodated in this casing I an electromotor, the stator of which is denoted by 3 and the rotor of which is denoted by 4, and which electromotor is connected to a power line by means of the terminals 6, 5 and 6", which are arranged `in a box 5 on the outside of the casing I. The rotor 4 of the electromotor is mounted and keyed on aA sleeve 1, through which a shaft 8 is passedso as to be freely rotatable, one end of which shaft is mounted by means of a ball bearing 8' in the lid 2. One end of the vsleeve 1 is mounted in the lid 2 in a ball-bearing 9 and the other end is mounted in a needle bearing II) in the hub of cone disc II which is rigidly mounted'on the end of the' shaft 8. In iront of the needle bearing I0, the sleeve 'I has an eccentric extension I2, on which a ring I4 is mounted on two-ball bearings I3 and I3. Ring I4 has an external ring of teeth I5 and an- 3 internal ring of teeth I 6. For the purpose of balancing the mass cf the eccentric extension I2, an eccentric ring I2' is fixed on the sleeve 1 between the ball bearings I3 and I3'. The external ring of teeth I5 of the eccentrically mounted ring I4 engages with an internal ring of teeth I1 of a bell-shaped supporting ring i8, which is provided inside the casing I, and a rotary toothed wheel I9iwhicli is mounted on the sleeve 1 by means of a ball bearing 1. The rotary toothed wheel I9 engages in the supporting ring I9 and it i has, on its periphery, a somewhat reduced flange 20 whi-ch is coated with a brake lining 2i.

The internal ring of teeth I6 of the ring l4 engages with a ring of teeth 22 on the hub of the cone disc II. Fixed to the supporting ring IB by means of screws 23 is a sheet-metal casingk 24 which encloses the rotary toothed wheel I9. The open end of casing 24 through which the sleeve 1 passes, is closedby a packing 25. Acting jonthe ball bearing 9, the outer ring of which i'sudisplaceably,mounted in the lid 2 and which, isfsecured on the sleeve 'I by a springwasher 26, against axial displacement, is an annularpressure plate '21 which has two, inwardly extending projections 28v which, lie in an` outwardly* open chamber of the lid 2. This pressure. plate 21 is acted uponby a compression spring 29 which bears lagainst a screw-threaded ring 39 which is'Y arranged, so as to be axially displaceable but secured against rotation by means of a projectionA3I, in a casing 32 which closes the outside of the chamber of the lid 2. The threaded ring 30 is screwed on to a threaded sleeve 33 which is mounted in the casing 32 in av ball bearing 34. An adjusting wheel 35; which is provided with'v a,scaleis connected with the threaded sleeve 33 by means of a screw 36. The open end ofthe casing 32 is closed by a packing 31 which slides on the hub of the adjusting wheel 35. A packing 38 is inserted inside the axial opening of -the lid 2, through which opening thev sleeve 1 and the shaft S pass. Bearing against a plate 39, which is likewise inserted into this opening, is"a compression spring 49 which acts upon the the'ball bearing 9 and tends to push it, together with the sleeve 1, outwards, i. e., in the embodiment shown, to the right.

On the rotation Of the rotor 4 and, consequently, of the sleeve 1, the external ring of teeth I5 ofthe ring I4 rolls on the internal ring of teeth I1 of the toothed wheel I9, with the result that the ring I4 is rotated. By meansof itswinternal'v ring of teeth I6, which engages the ringof teeth 22 of the cone disc II, the latter is likewise rotated. This driving arrangement is nothing more than a reduction gear by means of which the rotation of the rotor 4 is transmitted reduced lto the cone disc II. The loading of` the compression spring 29, which can be regulated-gb`y means of `the adjusting Awheel 35, effectsthe pressing of the flange 28 of the toothed wheel I9 against the supporting ring I8. There is thushprovided a preventive against overloading,V sincegthe toothed wheel I9 is no longer kept stationary but rotates when the transmission torque' exceeds a given value. If the compression'spring 29 is completely relieved by means of the'adjusting hand lwheel 35, the sleeve 1 and, with it, the toothed wheel I 9 are displaced in sncli a manner by the action of the compression. splicing', 4D" that the brake lining `2| of the flange Zis lifted from the supporting ring AI 8. Thus, an idle'running is produced. In this Way, the trailsmission torque can be adjusted from approximately zero up to a maximum value.

The other end of the casing I, which,v end is opposite the lid 2, is closed by a lid 4I in which the driven shaft 44 is mounted on ball bearings 42 and 43. A cone disc 45, which is symmetrical with regard to the cone disc Il, is mounted on the end, in the casing AI, of this shaft 44 which is co-axial with the shaft 8.l 4

In the lid 4I, the shaft 44 is closed outwardly byj a packing 46 and inwardly by a packing 41. Obviously, *ai* reduction gearing could be provided also between the cone disc 45 and the shaft 44.

The transmission of the rotary movement of the driving-side cone disc II to the driven-side cone disc45uis effected by means of a frictionwheel transmitting device, which is arranged in the interspace between these cone discs II and 45'and which is constructed in the manner to be described. v Y

The casing I has at the top in its central part,

i. Ie., above the cone discs I I and 45, arrapertureY which` isA`clolsedl byv a lid 48. On the'un'der'side of this lid 48 there is provided aguide, isparallel to the base planes of4 the cone discs I'I and A45 vand in which ytwo roller-S5!)` are guidedsoasto be rotatable about the axis of the'guide 49`and tovb'e displaceable in the latter. In'thsfe'V connected together by means of screws 55. In

an inner ball race of the ball bearing 53 there is fixed a disc 51, which has a friction-bead 59' onv its"outside surface which faces the cone disc 45. In the inner ball race of the ball bearing 54, there is mounted, so as to be axially displaceable, a disc 59'which has a friction-bead 6U on its outside surface, which faces the cone disc II. A journal 6I of a clutch kmember is Co-axially mounted in the kdisc 51. On this journal 6I there is mounted inside the disc 51 a part 62, which is bent off and on which rests a flange $3 which has a sector 54 which is connected by screws with the disc 5U. In the same way,` the pin 65 of a similar clutch member, which likewise has a bent off part 66, on'which rests a flange B1 with a sector E8, which is connected with the disc 51 by means of screws. These two clutch members engage with each other in such anmanner that the bent off part 66 of one clutch y. member liesin the ysector 64 of the other clutch member and vice versa-and theflanges 63 and 61 engage on the inside. The flanges 63 and S1 have on their peripheries the collars 69' and 19 respectively, between which a compression spring 1I is inserted, which causes the clutch member insertedinto the disc 59 and; with it, the disc 59 itself to be pressed away from the disc 51, i. e., towards the cone discv I I. On their engaging surfaces, theflangesl' and 61 have cams' 12 and 13 respectively, which are bounded and 60 to the cone discs 45 and Il, and thus ensures the starting of the gear. During the operation of the gear, the cams 12 and 13, which engage in each other and are bounded by screw surfaces of corresponding pitch, effect a pressing apart of the clutch members, and, consequently, of the discs 51 and 59 with their frictionbeads 58 and 60, in dependence upon the magnitude of the transmitted torque, so that the'pressing of the friction-beads 58 and 60 to the cone discs and 45 is always eiected automatically independently of the direction of rotation ofthe gearing and in accordance with the momentary requirements, with the result that, on the one hand, slip-free transmission of the rotary movement is assured and, on the other hand, excessive wear `of the cone discs I and 45 and ofthe friction-beads 58 and 60 are avoided. The flanges 63 and 61 instead of being connected with the discs 59 and 51 respectively by screws,'could be provided on their peripheries with screw threads and screwed into corresponding screw threads provided in the discs 59 and 51 respectively.

For the purpose of altering the gear ratio of the friction-wheel regulating gear, the sliding members 50 and, consequently, the whole frictionwheel transmission device which is arranged between the cone discs and 45 are displacedV in their guide 49. This can be effected by means of, for example, a screw spindle, which is axially undisplaceably mounted in a part of the casing. This displacement is advantageously effected with the aid of a device such as is represented in the drawings and now to be described.

In the lid 48, oiTset to the guide 49, there is iixed a journal 14 on which a sleeve 15 is xed. Rigidly connected with this sleeve 15 is a disc 16, which has a ring of teeth 11, with which an internal ring of teeth 18 of a ring 19 engages. kThe ring 19 is mounted so as to be freely rotatable on an eccentric which is formed by the hub 80 of a handwheel 8|, which is mounted by means of a ball bearing 82 on the sleeve 15, so as to be freely rotatable. It has an external ring of teeth 83, which engages with an internal ring of teeth 84 of a disc 85, which is mounted so as to be freely rotatable on the sleeve 15 and in a ball bearing 88. With the aid of this disc 85, a crank disc 83, which is likewise mounted in the ball bearing 86, is rigidly connected by screws 81, which crank disc has a crank 89 that is movable in a space in the lid 48. On this crank 89 there is mounted a vcrank pin 90 on which is mounted a connecting rod 9|, the other end of which is hinged to the upwardly projecting narrowed end of the journal 4l in one roller 40. On rotating the handwheel 8|, the ring 19, which is mounted on the eccentric hub 80 of the handwheel 8|, rolls on the ring of teeth 11 and of the stationary disc 16 and through its outer ring of teeth 83 and the inner ring of teeth 84 of the disc 85, which inner ring of teeth is in engagement with the outer ring of teeth 83, rotatesthe disc 85. This driving arrangement is nothing more than a revolution-reducing device which is self-stopping, so that the shifting of the bearing ring by any forces acting thereon is rendered impossible. yThe crank disc 88 is driven and,`by means of the connecting rod 9|, the journal 5| with its roller and, consequently, the whole friction-wheel transmission device are displaced in the guide 49. The limiting positions are determined by the crank 89 'and they correspond to the outermost and the innermost points of contact of the friction-bead 60 on the conical-surface une of the cone disc u 01- of the friction-bead 5s on the conical-surface line of the cone disc 45. The result of the circumstance that the displacement ofthe friction-wheel transmission device is effected through a crank is that this displacement does not take place uniformly between the limiting positions, but as a sine function. This has the great advantage that, near the limiting positions of the friction-wheel transmission device, where a small displacement corresponds to a great alteration in the gear ratio of the gearing, there corresponds, to a particular rotation of the handwheel 8|, a correspondingly smaller displacement of the friction-wheel transmission device than an equally large rotation of the handwheel 8| in the central part of the range of regulation. A balance is consequently created in such a manner that, to a particular rotation of the handwheel 8|, there corresponds an approximately equal alteration of the gear ratio in the whole range of regulation of the gearing. The two limiting positions correspond to gear ratios of 1:7 and 1:-7, that is to say the number of revolutions per minute of the cone disc I can be transmitted to the cone disc 45 within the limits 1:'7 stepped up or stepped down. Accordingly, in the case represented, there is produced, with 2,800 revolutions per minute of the electromotor and with a stepping down of about 5.811 on the driving side, a range of regulations of about 3,500 to '10 revolutions per minute. For the shifting from one into the other limiting position, about four revolutions of the handwheel 8| are necessary in the `case of the device represented. In this way a very accurate adjustment is rendered possible. Naturally, the adjustment gear ratio may diifer as desired. Advantageously, there is provided on the disc a scale or like indicating device (not represented in the drawings), on which the particular adjustment of the gear ratio of the friction-wheel regulating gear can be read by means of an index provided on the lid.

Owing to the circumstance that the rollers 50 are rotatable about the axis of the guide 49, the result is obtained that the friction-wheel transmission device can be rocked somewhat between the cone discs and 45, so that the frictionbeads 58 and 6|) can always bear with certainty on the cone discs and 45 with the same pressure.

On the periphery of the cone disc there is arranged a fan blade device 92, which sucks air through an aperture 93 provided in the casing and expels it through an aperture 94 provided in the lid 2, or vice versa, in accordance with the direction of rotation. In this way, the whole casing l is ventilated.

` `A special advantage of the friction-wheel regulating gear, according to the invention, is to be seen in the fact that its driving-side part, its driven-side part and the friction-wheel transmission device between these parts each form a structural unit. In this way, not only are the whole construction and assembly simplied, but the possibility is created of tting both the driving-'side part as well as the driven-side part as desired in a machine, or to construct them as a part of such a machine. It is unnecessary for the casing to he constructed as a unitary structure; on the contrary, it may be composed of two or three parts.

What I claim is:

1. A friction-wheel regulating gear comprising two coaxial spaced cone discs, one of said cone discs being adapted tobe driven by a driving machine and the other of said cone discs being adapted to drive a driving shaft,`a friction-wheel transmission. device'adapted to alter t'hefgea'rl ratio andV displaceably arranged between said discs', thedriving-side'part and the' driven-sidepart of saidregulatinggear and said friction-wheel transmission device being each constructed asa structural unit, said-friction-wheel transmission de- Vicecomprisingtwo discs each with a frictionbeadand coupled together with regard to rotationl but axially displaceabie in relation to `each other, one of said beads lying on a point ona conical-surface line of the driving-side cone disc and the-other of said beads lying on a point on a conical-surface line of the driven-side` cone disc which latter conical-surface line lies opposite and vparallel to said conical-surface line of the drivingside cone disc7 spring .means for urging said beads apart and against said two cone discs, Contact of saidfbeads with said cone discs being adapted to take place on said conical-surface lines, a supporting ring in which said discs are mounted, rollers on which said supporting'rin'g is arranged, a` guide which is parallel to said conical-surface lines'of said cone discs andi in which said rollers are' adapted to be displaceably guided, and a shifting device adapted to displace said rollers in said guide within two limiting positions and thus'to alter the gear'ratio'.

2. A' friction-wheel regulating gear comprising two coaxial spaced cone discs, one f said cone discs being adapted to be driven by a drivingmachine and the other of saidcone discs being adapted to drive a drivingV shaft, a friction-wheel transmission device adapted# to alter the gear ratio andi displaceably arranged between said discs, the driving-side part and the driven-side part of said regulating gear and said friction-wheel transmission device being each constructed as a structural unit, said friction-wheel transmission device comprising two discs each with a frictionlieadvv and coupled' together with regard to rotation but axially displaceable in-re'lation to each other, one of said beads lying on a point on a conical-surface line of the driving-side cone disc and the other of said beads lying on a point on a conical-surface line ofthe driven-side cone disc which latter conical-surface line lies opposite and parallel to said conical-surface line of the driving-side cone disc, spring means for urging said beads apart against said two cone discs, contact of said beads with said cone discs lbeing adapted toA take place on said conical-surface lines, a supporting ring in which said discs are mounted, rollers on which sai-:l supporting ring is arranged, a guide which is parallel to said conical-surface lines of said cone discs and in which said rollers are adapted to -be displaceably guided, a shifting device adapted to displace said rollers in said guide within two limiting positions and thus to alter the gear ratio, a clutch member rigidly connected with each of said displaceable discs, and a cam ior each of said clutch members whereby said clutch members are caused to engage in each other, said cams being bounded by screw surfaces which continuouslymerge into each other and lie on each other and said clutch members being adapted to clutch said two displaceable discs in such a manner that said clutch members are pressed apart by means of the screw surfaces of saidcanis in dependence upon the magnitude` of the transmitted torque.

3. A' friction-wheel regulating gear comprising two coaxial spaced cone discs, one of said cone discs rbeing adapted' to be driven by a driving machine and the other of said cone discs being ,adapted to drive a driving shaft, afriction-wheel 8 transmission. device adapted to alter '.the gear rau tio" andi displace ably; arlra'nged betweenf saidf dises, the driving-sidefpartand the driven-sidepart o! saidregulatingigear and said friction--wheeltrans missioni device being each constructedv as astructural unit, said` friction-wheel transmission de= vice comprisingtwo'discs eachfwith alfriction bead and coupledtogether with regard to rota.- tion butaxially displaceable in vrelation'ito each other, one of said beads lying on' a point'fon' a conical-surface line 'of thef driving-sidevr cone disc and the-other ofl said beads lyingon 'a= point on a conical-surf ace line ofthe* driven-sidecone disc which latter conical-surface line'lies opposite and parallel toI saidfconical-surface line of the driving-side" cone disc, spring means for urgingv said beads apart againstsaid two cone'discs, contact of said bea-ds withl said con'e discs' being adapted to takeplace-on said conical-surfaceflin'es; asupporting-ring in which saiddiscs' aref mounted, rollers oli-which saidv supporting ring is arranged', aguide which is parallel to said conical-surface lines ofsaid cone discs and in which saidV rollers are adapted to be displacea'bly'guided, a shifting device adapted to displace said rollers in" sai'd guide within two limiting'positions and thus to alter the gear ratio, acrank disc' mounted on the part containing said guide and offset to--said guide, an operating member fordriving said crank disc,` a: crank pin on said crank disc, and, for-dis'- placing said rollers in said guide, a connecting rod hinged, on the one hand, to a journal of oneof the rollers and, ony the other hand, to said crank pin.

4. A friction-wheel regulatinggear according to claim 2, comprising a crank disc mountedon .the part containing said' guide and oifset tosaid guide, an operating member for driving sai'd crank disc, acrank pin on said crank disc; and', for displacing said rollers in said guide, av connecting rod hinged, on the one hand, to a journal of one of the rollers and, von fthe other hand, t0 said crank pin.

5. A friction-wheel regulating gear' according to' claim 3, comprising a self-stopping reduction gear 'between said operating member and said `crank disc.

6.- A friction-wheel regulating gear comprising two coaxial spaced' cone discs, one of said cone discs being adapted' to be driven by a driving machine and the other of said cone discs lbeing adapted to drive a driving shaft, a friction-wheel transmission device adapted to alter the gear ratio and -displaceably arranged between said discs, the driving-side'- part and 'the drivenside part of said regulating gear and said friction-wheel transmission device being each constructed as a structural unit, said friction-wheel transmission device comprising two discs'each with a friction-bead and coupled together with regard to' rotation but axially dsplaceable in relation to each other, one of said beads lying on a point on la conical-surface line of the driving-side cone disc' `and 'the other of said beads lying' on a point on a conical-surface line of the driven-side cone disc which latter conical-surface line lies opposite and parallel to said-conllcal-'surface line of the driving-side cone disc, spring means for urging said beads' apart yand against said two conediscs, contact of saidbeads with said `cone discs being adaptedto takey place on said conical-surface'lines, a supporting ring in which said discs are mounted, rollers on which said supporting ring is arranged, a guide which is parallel to said conical-surface lines of. said cone discs and lin which said. rollers areadapted to be displaceably guided, and a shifting device adapted to displace said rollers in said guide within two limiting positions and thus to alter the gear ratio, said rollers being rotatable about the axis Iof said guide in such a manner that said supporting ring is rockable between said two cone disc-s with said displaceable discs.

'7. A friction-wheel regulating gear compristWo coaxial spaced cone dis-cs, one of said cone discs being adapted -t'o be driven by a driving machine and the other of said ycone discs being adapted to drive a driving shaft, a friction- Wheel transmission device adapted to alter the gear ratio and displaceably arranged between said dis-cs, the driving-side part and the drivenside part of said regulating gear and said friction-wheel transmission -device being each constructed as a structural unit, said friction-wheel transmission device comprising two discs each with a friction-bead and coupled together with regard to rotation but axially displaceable in rotation to each other, one of said beads lying on a point on a conical-surface line of the driving-side cone disc and the other Iof said beads lying on a point on a conical-surface line of the driven-side cone dis-c which latter conical-surface line lies opposite and parallel =to said conical-surface line of the driving-side cone disc, yspring means for urging said beads apart and against said two cone discs, contact of said beads with said cone discs being adapted to take place on said conical-surface lines, a supporting ring in which said discs are mounted, rollers on which said supporting ring is arranged, a guide which is parallel to said conical-surface lines of said cone discs and in which said rollers are adapted 'to be displaceably guided, a shifting device adapted to displace said rollers in said guide Within two limiting positions and thus to alter the gear ratio, the shaft of at least one cone disc 4 being mounted so as to @be axially d-isplaceable, a pressure plate against which said shaft bears, said pressure plate being arranged so as to be 10 `axially displaceable, a closed chamber behind said pressure plate `and an elastic buffer in said closed space.

8. A friction-wheel regulating gear according 5 to claim 2, the shaft of at least one cone disc being mounted so as to be axially displaceable, said friction-wheel regulating gear lalso comprising a pressure plate against which said shaft ibears, said pressure plate being arranged so as to be axially displaceable, a lclosed chamber behind sai-d -press-ure plate and an elastic buffer in said lclosed space.

9. A friction-wheel regulating gear according to claim 1, comprising a casing for said gear,

said casing having apertures at the ltwo ends thereof and a fan blade carried on the periphery of one of said cone discs and adapted to produce through said apertures a current of air for ventilating said gear.

10. A friction-wheel regulating gear according to claim 2, .comprising a casing for said gear, said casing having apertures at the two ends thereof and a fan blade carried on the periphery of one of said cone discs, and adapted to produce through said apertures a current of air for ventila-ting such gear.

ERNST KREBS.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,127,166 Beugler Feb. 2, 1915 1,229,401 Black et al June 12, 1917 2,019,006 Ferrari Feb. 1, 1934 A2,325,323 Johnson et al July 27, 1943 FOREIGN PATENTS o Number Country Date 824,593 France Nov. 10, 1937 

